Electrical heating pad

ABSTRACT

An electrically conductive sheet of flexible material includes conductive particles and channel-shaped electrodes are provided on opposite ends and are connected by lead wires to a power source. A flexible insulating envelope is bonded to and protects the conductive sheet. Holes may be provided in the conductive sheet to facilitate bonding between the protective cover and the conductive sheet. The conductive particles may be carbon and the sheet may be formed from fibrous material or rubber. The protective sheet may be molded from plastic or rubber having a very low carbon content.

United States Patent [1 1 Michaelsen ELECTRICAL HEATING PAD [75]Inventor: Dwight W. Michaelsen, Columbus,

Nebr.

[73] Assignee: Dale Electronics, Inc., Columbus,

Nebr.

22 Filed: Dec. 6, 1971 2 11 Appl. No.: 204,860

521 U.S. 01...; 219/s 28', 2197541, 2'19/543,

219/549, 338/212 [51] Int. Cl. 1105b 3/36 [58] Field of Search 219/211,212, 213,

[56] References Cited UNITED STATES PATENTS 2,458,184 1/1949 Marick219/543 X 3,344,385 9/1967 Bartos et a1 338/212 3,535,494 10/1970Armbruster.. 219/528 3,558,858 1/1971 Luger, Jr. 219/528 3,627,98112/1971 Kuhn 219/549 X 3,697,728 10/1972 Stirzenbecher 219/548 2,473,1836/1949 Watson 219/543 2,688,070

8/1954 Freedlander 219/528 [451 July 31, 1973 Glicksman 219/528 X3,281,579 10/1966- 3,367,851 2/1968 Filreis et al. 204/2 3,283,28411/1966 Eisler 338/212 2,938,992 5/1960 Crump 219/528 3,385,959 5/1968Ames et 219/549 2,559,077 7/1951 Johnson et a1..... 219/543 2,952,7619/1960 Smith-Johannsen.. 219/541 3,359,524 12/1967 Gallacher et a1.219/528 X Primary Examiner-,-Volodymyr Y. Mayewsky Attorney- Zar1ey,McKeejtitThomte 1 I [5 7 ABSTRACT An electrically conductive sheet offlexible material includesconductive particles and channel-shapedelectrodes are provided on opposite ends and are connected by lead wiresto a power source. A flexible'insulating envelope is bonded to andprotects the conductive sheet. Holes may be provided in the conductivesheet to facilitate bonding between the protective cover and theconductive sheet. The conductive particles may be carbon and the sheetmay be formed from fibrous material or rubbeLThe protective sheet may bemoldedfrom plastic or rubber having a very low carbon content.

1 Claim, 2 Drawing Figures ELECTRICAL HEATING PAD Portable heaters arecommonly used in and out of doors. Inside they may be used for a desktop warmer, desk foot warmer, foot stool warmer or for heating pads.Winter conditions outside make them desirale for windshield deicers,seat warmers and cat and dog house warmers.

One of the most important uses is for maintaining a battery at theoptimum temperature level to maximize the battery power available forstarting engines.

The heating pad of this invention contains no wires or ribbons and willnot develop hot spots and burn out: There is basically nothingtobreakfandcanKbecome partially damaged and still function. Theelectricalproperties remain unchanged by the unit being exposed to dampness andthen redrying. Further, repeated flexing has little effect on theelectrical properties. The conductive element has uniform conductivityfrom point to point over the element regardless of the direction ofcurrent flow. Also, very important is the fact that the heater unit canbe produced more inexpensively than a conventional wire-wound heaterunit.

The heater unit of this invention includes a sheet of conductivematerial which is highly flexible and has channel-shaped electrodes atopposite ends connected to lead lines adapted to be connected to a powersource.

This invention consists in the construction, arrangements andcombination of the various parts of the device, whereby the-objectscontemplated-are attained as hereinafter more fully set forth,specifically pointed out in the claims, and illustrated intheaccompanying ally in FIG. 1 by the reference numeral 10. The heatingvpad includes a flexible electrically conductive sheet 12. Suitablematerials include rubber having carbon particles impregnated therein insufficient quantities to make the sheet electrically conductive.Temsheet produced by Armstrong Cork Company, Lancaster, Pennsylvania, isalso acceptable. A channel-shaped electrode 14 is secured to theopposite ends of'the sheet 12 and bonded in place by any suitable meanssuch as the staples l6, seen in FIG. 2. The electrodes 14 are preferablybrass.

An electrical lead line 16 includes one line 18 connected to oneelectrode while the other line 20 is connected to the opposite electrode14. A rivet and solder connection 22 is used for connecting the leadline wires I envelope 24 of insulating material such as rubber hav-' ingno carbon or very little carbon. A flexible plastic may also be used.The conductive sheet 12 is com-- pletely sealed within the protectiveenvelope 24 by a molding or vulcani zing process. Openings 26 are pro-.

vided in the sheet 12 to further facilitate the bonding of the envelopematerial to the conductive resistance sheet 12. I

I I It is seen in FIG-2 that'the electrodesl4-are inwardly, j.

spaced from the outer adjacent edges of the envelope 24 and thus provideextra protection at the ends of the heating pad and in particularlyprovide flexible support for the electrical lead line 16 to minimizestress and strain at the electrodes 14.

It is seen that the use of synthetic natural rubber or plastic in theenvelope 24 provides resistance and protection against the action ofsolvents, acids, and moisture making the heating pad very suitable forindustrial applications including the warming of batteries. "It isfurther seen that there is essentially nothing to break in thisheatingpad as there are no wires or ribbons to break. Further, the"carbon impregnated resistance sheet of the battery heater of thisinvention can be produced more economically than a wound-wire battery'heater.

I claim: Q 1. An electrical heating pad comprising,

an electrically conductive sheet of flexible material an envelope ofelectrically insulative flexible material molded onto and enclosing saidsheet, said envelope having a size larger than said sheet so that said.

sheet is completely enclosed therein, t said conductive sheet having aplurality of openings formed therein which receive the flexible materialsaid conductive sheet being stapled together. i 4

, a: k a: a: e

1. An electrical heating pad comprising, an electrically conductivesheet of flexible material having electrically conductive particlesuniformly disposed throughout said sheet, an electrode secured toopposite ends of said sheet, said electrodes being channel shaped andthe opposite edges of said conductive sheet are received in saidchannel-shaped electrodes, an electrical lead wire connected to each ofsaid electrodes, and an envelope of electrically insulative flexiblematerial molded onto and enclosing said sheet, said envelope having asize larger than said sheet so that said sheet is completely enclosedtherein, said conductive sheet having a plurality of openings formedtherein which receive the flexible material of said envelope to bond theenvelope to said conductive sheet said channel-shaped electrodes andsaid conductive sheet being stapled together.